Flow control devices which provide brake airline locks and the like for vehicles are well known. However, many of these are expensive to manufacture due to their complicated designs and numbers of parts involved and others, while adequate, are open to improvement in this art.
U.S. Pat. No. 3,682,195 of Aug. 8th, 1972, CVETKOVICH, discloses a wheel lock for a vehicle comprising a valve means that is interposed in the brake fluid line of the vehicle, the lock including a key-locked camshaft. Turning the key lock operates the camshaft which urges the valve means toward a closed position to block fluid flow through the brake line.
U.S. Pat. No. 3,617,663 is another example of the prior art and shows an anti-theft lock for vehicle brakes and ignition systems which uses a key-operated cam to release brakes of the vehicle.
The U.S. Patent to MURRAY, U.S. Pat. No. 4,543,984 of Oct. 1st, 1985, discloses a valve means mounted on a trailer connected with a tractor truck, the valve means being interconnected in the air line to maintain brake-on air pressure in the line while the trailer is parked. The valve means has a locking handle to inhibit trailer theft.
The Patent MAXWELL, et al U.S. Pat. No. 3,998,495 of Dec. 21st, 1976, illustrates a control valve which selectively can establish a connection between a spring applied parking brake in an air-brake vehicle and either the parking brake air reservoir or the exhaust port of the control valve. The control valve incorporates a lock that enables an operator to secure the valve in the position in which the parking brakes are applied.
The present invention provides novel and unobvious differences over the prior art such as U.S. Pat. No. 3,998,495. The locking mechanism shown in the drawings is an *ACE or tubular type cylinder to control the position of a cam which acts upon locking means in the unit. However, it will be appreciated that the device can be fitted with any one of a variety of high security type cam lock cylinder such as *Medico, *Abley or the like. In a locked position, the cam forces the locking means into operative positions in the device. In the prior art such as U.S. Pat. No. 3,998,495, the patentee uses a Wafer-type cylinder which controls the position of a bolt that secures the valve in the open or closed positions. FNT *TRADEMARK
The present invention incorporates means to ensure that in the event that an operator leaves his key in the lock and in the "unlocked" position, the valve means will return and stays in an "open" position. This will prevent accidental closing of the valve which could result in the application of the vehicle brakes. This is a definite safety feature of the present invention over the prior art.
Moreover, the elements in the present invention are so designed that the device will not bleed off downstream pressure in an air-brake system when the valve means is moved to a "closed" position. To lock the brakes on in a vehicle an operator would look the valve in a closed position and then set his emergency brakes by closing the emergency brake valve already incorporated in the truck brake circuitry. The emergency brake valve bleeds off downstream pressure. This emergency brake valve is a required component in most air-brake systems.
With the present arrangement, a locking of the emergency brakes would be a deliberate, two-step procedure which again increases the safety of the system.
Prior designs such as U.S. Pat. No. 3,998,495 include an exhaust port to bleed off downstream pressure when the valve is closed thereby duplicating the purpose of the existing emergency brake valve.
The present invention goes a long way to prevent accidental application of the brakes due to the inability of the flow control device according to the invention to bleed off downstream pressure and also due to the provision of the means that biases the valve means to the operative or open position.